Auditory Cognitive Function Among Individuals With Schizotypal Traits

Schizotypy represents a personality organization characterized by schizophrenia-like symptoms reflecting increased genetic risk for schizophrenia-spectrum disorder,and constitutes a background for the development of psychotic illnesses.Schizotypy comprises “cognitive-perceptual”,“interpersonal” and“disorganized” factors — representing schizophrenia’s positive,negative,and disorganized facets,respectively.Behavioral and neurobiological researches showed that some schizophrenia-related cognitive deficits and processing abnormalities exist in individuals with high schizotypy,despite attenuated magnitude.However,other evidence suggested an association between schizotypy and creativity as well as openness to experience.The study on schizotypy is helpful to explore both pathogenic and protective factors of schizophrenia-spectrum disorder,and is valuable for the underlying mechanisms of psychopathological development.Auditory dysfunction is observed frequently among patients with schizophrenia-spectrum disorder.Deficits in basic sounds perception and high-level auditory processes have been discovered in people with schizophrenia and are considered systematic auditory impairments of various auditory hierarchical levels.However,evidence on whether auditory cognition deficits exist among individuals with high schizotypy is rare and mixed.Results of basic auditory perception from samples with high schizotypal traits have been inconsistent.In addition,other evidence suggests an association between schizotypy and creativity as well as openness to experience.Music is considered as a phenotype of creativity on auditory domain,and previous studies have shown that individuals with music occupations have higher schizophrenia-like symptoms.These seemingly contradictory results are important for understanding the pathogenesis of schizophrenia and highlight the possibility of a compensatory mechanism.Based on the theory of auditory hierarchical process system,five studies,consist of nine experiments,were designed in this dissertation.The auditory acuity,the auditory event related potentials(ERPs)and the autonomic responses(skin conductance and heart rate)were measured combined with behavior assessment methods.The basic sounds perception and music process were investigated systematically among non-clinical individuals with high schizotypal traits(Schizotypy group,SP),and compared with results from the matching participants with low schizotypy(Control group,CG).(1)Experiment 1 & 2 found that individuals with high schizotypy had elevated acuity in auditory discrimination,specifically in auditory temporal perception tests(the pure tone duration discrimination test examined the temporal perception of sounds,while the white noise gap discrimination test examined the temporal perception of silence).This heightened sensitivity was validated in the regression analysis in the CG between the threshold of tone duration discrimination and cognitive-perceptual scores,which presented the positive facet of schizotypy.There was a significant binomial distribution of schizotypy and auditory duration sensitivity.(2)Experiment 3 & 4 found significant larger pitch and duration MMN amplitudes among individuals from SP,reflecting the enhancement of bottom-up detection on sounds.The duration MMN amplitude on large deviation condition was positive associated with schizotypal traits in CG;however,the pitch and duration MMN amplitudes were correlated negatively with schizotypal traits in the SP.There was a significant binomial distribution of cognitive-perceptual factor and the duration MMN amplitude on large deviation condition.In addition,a significant duration P300 reduction was observed in the SP,reflecting the weaker top-down process on temporal deviation of sounds among individuals with high schizotypy.The pitch and duration P300 amplitudes were negative correlated with the interpersonal factor in the CG;however,the duration P300 amplitude was associated positively with the disorganized factor in the SP.(3)Experiment 5 revealed that individuals with high schizotypy had improved musical ability,especially in the musical rhythm and melody contour cognition.This improvement perhaps represent the inherent musical aptitude among individuals with schizotypal traits.(4)Experiment 6 & 7 revealed that individuals from the SP had better performance in the harmony emotion recognition task,and had higher accuracy in the identification of musical excerpts’ emotion.In the CG,the accuracy of peaceful musical emotion recognition is associated positively with schizotypy’s cognitive-perceptual and disorganized dimensions;however,the schizotypy’s cognitive-perceptual factor was correlated negatively with the identification accuracy of harmony emotion recognition and musical excerpts’ happy emotion in the SP.In addition,there was a significant binomial distribution of the identification accuracy of peaceful musical emotion and the schizotypal traits.(5)Experiment 8 & 9 found greater increase of emotional valence and stronger evoked skin conductance activity during the happy classic music listening among participants with high schizotypy.In the CG,the skin conductance response was correlated positively with the schizotypal traits;however,the increment of emotional valence was marginally associated negatively with disorganized facet of schizotypal traits in the SP.The correlation between the skin conductance response and schizotypy,as well as the correlation between the increment of emotional valence and schizotypy,were both showed significant binomial curve tendency.Based on above results,the following conclusions could be drawn:(1)There is systematical improvement of auditory function among non-clinical individuals with high schizotypy,represented by the elevated auditory acuity,improved musical aptitude,better musical emotion identification and stronger response to music listening experience.This improvement trend was supported by the associations between indicators of auditory process and schizotypy in the CG.These results suggested that non-clinical individuals with high schizotypy may be more sensitive to the deviation of sounds’ pitch and duration,and had improved ability in music process which relies on bottom-up detection of auditory clues.They also benefited more from happy music experience,compared to the CG participants.(2)In the SP,most indicators of auditory process were associated negatively with schizotypy.In addition,the links between various indicators of auditory process and schizotypal traits showed significant binomial distributions.Together,these results suggested that,with the increase of schizotypy,especially the positive facet,the abnormalities in auditory domain may not show a linear variation.A possible explanation is there may be “inverted-U/J” relationships between schizotypy and some auditory functions.(3)Although the bottom-up auditory process may be enhanced with the non-clinical and mild schizotypy,the top-down process is poorer with the increase of schizotypal traits.However,this negative association between the top-down auditory process and schizotypy showed an inversion in the disorganized dimension when the schizotypy-symptom was extremely high.These results suggested that the schizotypy may have different effects on bottom-up and top-down auditory process.